1. Field of the Invention
The present invention relates to a technique of reducing the phenomenon known as color bleeding, which occurs when color images are formed on plain paper (having a surface which is not covered by any pigments or coatings), and a technique of producing water-resistant ink images, and more particularly to a liquid composition which can be applied to an ink jet image-forming process, an ink set obtained by combining an ink with that liquid composition, and image-forming methods and apparatus to which the liquid composition and ink set can be applied.
2. Description of the Related Art
In an ink jet recording process, recording is conducted by ejecting ink in the form of a small droplet and thereby attaching it to a recording medium, such as paper. Particularly, in an ink jet recording process of the type which employs, as discharge energy supply means, an electrothermal transducer to apply heat energy to ink and thereby generate a bubble which results in discharge of an ink droplet, a high-density multiple-orifice recording head can be readily manufactured, thus enabling high-resolution and high-definition images to be recorded at a high speed. Such an ink jet recording process has been disclosed in, for example, Japanese Patent Publication Nos. Sho 61-59911, Sho 61-59912 and Sho 61-59914.
Generally, ink employed in conventional ink jet recording methods contain water, which is its major component, and a water soluble high-boiling point solvent, such as glycol, for preventing drying or clogging of the nozzle. When recording is conducted on plain paper using such an ink, sufficient fixing may not be obtained or non-uniform images may be generated. It is believed that the latter problem occurs due to non-uniform distribution of filler or sizing agent on the surface of the recording paper. Further, in the case of color recording, inks of a plurality of colors are placed successively on top of ink of a certain color before the ink of that certain color has been fixed. Thus, colors may spread or be mixed non-uniformly on the boundary of images of different colors (hereinafter this phenomenon is called bleeding), thus making produced images unsatisfactory.
To enhance the fixing property, Japanese Patent Laid-Open No. Sho 55-65269 discloses a method of adding, to ink, a compound which enhances permeability, such as a surface active agent, and Japanese Patent Laid-Open No. Sho 55-66976 proposes the use of ink mainly composed of a volatile solvent. However, in the former method of adding, for example, a surface active agent to the ink, although permeability of the ink into the recording paper is enhanced and hence the fixing property or bleeding of the ink is improved accordingly, a coloring material in the ink may also penetrate the recording paper, thus reducing the density and saturation of an image. In addition, ink may expand in a lateral direction, thus reducing the sharpness of an edge or the resolution of an image. In the latter method which employs an ink mainly composed of a volatile solvent, clogging of a recording head nozzle due to evaporation of the solvent may occur in addition to the problems encountered in the former method.
To overcome the aforementioned problems, it has been proposed to attach to the recording medium a liquid which improves attachment of the ink prior to ejection of the ink.
For example, Japanese Patent Laid-Open No. Sho 63-299971 discloses a method of performing recording on a recording medium with ink which contains an anionic dye after a liquid containing an organic compound having two or more cationic groups per molecule has been attached to the recording medium. Japanese Patent Laid-Open No. Sho 64-9279 discloses a method of performing recording on a recording medium with ink containing an anionic dye after an acid liquid containing, for example, succinic acid, has been attached to the recording medium; Further, Japanese Patent laid-Open No. Sho 64-63185 proposes a method of applying liquid which makes a dye insoluble prior to recording with ink.
Although any of the above-described methods contemplates improvement of bleeding or water resistance of images due to dye precipitation, bleeding which occurs between the color inks may not be sufficiently restricted, or the precipitated dye may be distributed on the recording paper non-uniformly, causing poor coverage on pulp fibers of the recording paper and reducing the uniformity of the images.